1. Field of the Invention
This present invention relates to a printing control system for controlling the time of a print-head to jet out an ink drop at different moving speeds.
2. Description of the Prior Art
The well-known print-head of the printing apparatus is driven by a motor to move back and forth. The print-head will go through a moving process of accelerating, uniform speed, and decelerating during the printing process. Because a certain distance exists between the print-head and the printing paper, when the print-head jets out an ink drop at different moving speeds, the position on the paper where the ink drop lands will also be different. If the print-head continues to jet out ink drops while the moving speed is being changed, the print quality will be affected by unbalanced ink density. Therefore, the printing margin of the printing apparatus of prior art is set corresponding to the moving speed of the print-head, so as to avoid the shifting of the landing positions of ink drops while the moving speed of the print-head is being changed.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of relative landing positions of an ink drop when the print-head 10 of the prior art jets out an ink drop 12 at different moving speeds. In FIG. 1, V1, V2, and Vh respectively represent different moving speeds; d1, d2, and dh respectively represent different positions where the ink drop 12 lands corresponding to V1, V2, and Vh, and Vp represents the jetting speed of the ink drop 12 which is jetted out by the print-head 10; L represents the distance between the print-head 10 and the printing paper. The position that the ink drop 12 is jetted out by the print-head 10 is set to be 0 which also changes according to different jetting speeds. The faster the moving speed, the longer the distance between the landing position of the ink drop 12 and the position 0.
Please refer to FIG. 2. FIG. 2 is a diagram about the relationship between the printing time and the moving speed of the print-head 10 in FIG. 1. In FIG. 2, the x-axis represents the printing time, and the y-axis represents the moving speed of the print-head 10. When the print-head is started to print, it will go through the moving process of accelerating, uniform speed, and decelerating; for example, the speed curve 20 of FIG. 2 includes an accelerating interval 22, a uniform speed interval 24, and a decelerating interval 26. In order to avoid the situation where unbalanced ink density affects the printing quality because the ink drop 12 jetted out by the print-head 10 lands at different positions corresponding to different moving speed, the printer can set the printing margin to be in the uniform speed interval 24. When printing in different number of dots per inch, the moving speed of the print-head 10 changes accordingly; therefore, different speed curves are generated. When the print-head 10 is set to print in the certain designated number of dots per inch, the moving speed of the print-head is Vh (the speed at the uniform speed interval).
Printers disclosed in the prior art increases the printing margin by increasing the length of the uniform speed interval 24 and decreasing the length of the accelerating interval 22 and the decelerating interval 26. However, the moving distance of the print-head 10 is restricted to the size of the printer's body, and the degree of increasing the length of the uniform speed interval 24 and decreasing the length of the accelerating interval 22 and the decelerating interval 26 is also confined to a certain extent. Therefore, upon the trend of miniaturizing printers, the method of increasing the length of the uniform speed interval 24 and decreasing the length of the accelerating interval 22 and the decelerating interval 26 has limitations.
In order to solve the above-mentioned problems, the present invention provides a printing control system and method thereof to improve printing quality while the print-head moves at different moving speeds and to further increase the printing margin.